The invention is directed to tires for bicycles, motorcycles and other two-wheeled vehicles, more particularly the invention is directed to a large section, lightweight, supple all terrain cycle tire with specially designed tread to provide low rolling resistance, high stopping traction, high cornering traction, high motive traction, and high off-angle traction with a high degree of self cleaning of the tread in all ground conditions, including wet or mud. In one preferred embodiment, one tread design is intended for the front or rear tire of the bicycle or motorcycle, and another tread design is specifically for the rear.
An all terrain cycle tired needs to perform the following functions:
1. protect the wheel rim from impact damage due to irregular surfaces or sharp objects that are encountered. PA1 2. provide a cushion or suspension function between the ground and the bicycle frame, to improve the ride comfort as well as to increase traction and reduce rolling resistance. PA1 3. provide adhesion to the ground surface for motive traction, braking, and cornering forces, and to resist slipping on angled surfaces. PA1 4. support the weight of the cycle and rider. This requires casing and tread layer of adequate strength and material to contain both the air pressure needed to perform the above functions and resist without damage the typical sharp rocks and so forth that may puncture or cut a weak tire. PA1 5. Provide a very light weight tire, for low rotating mass. This allows faster response for acceleration, steering, and suspension functions (smoother ride, better traction), as well as making it easier for the bike to climb uphill. PA1 6. Low rolling resistance is desired. This is needed in order to achieve the maximum speed and distance out of a limited amount of available energy. PA1 7. Very high cornering adhesion, with high consistency across differing types of ground conditions. PA1 8. Very good stopping traction, also with a high degree of consistency across varying ground conditions. PA1 9. Very high motive traction for the rear wheel, also with a high degree of consistency across varying ground conditions. PA1 10. Self cleaning design, such that dirt, mud or rocks do not remain adhered to the tread surface or lodged in the spaces between tread blocks.
In a high performance all terrain cycle tire according to this invention, additional factors are to be optimized.
Most of the high performance tires commercially produced appear to be designed for or at least they work best on a narrow range of ground conditions and in most cases for dry hardpack or dry loose material. They use relatively large tread blocks oriented across the direction of travel in the center of the tire and some narrower blocks oriented longitudinally on either side of the tire.
The tire contact patch is approximately an elongated ellipse along the centerline of the tire. The side blocks typically are not touching the ground on a flat level hard surface with normal loading and pressure. Most of the tires on the market have the center tread pattern (that which is in contact with the flat level hard ground) arranged with some kind of surfaces perpendicular or at a steep angle to (near perpendicular) the direction of travel so as to provide motive traction and braking, with little attention to cornering forces. The typical tire then has some tread oriented in a direction with the direction of travel on the sides of the tire casing for "cornering". These tires work well in dry dirt, somewhat loose material to hard packed, and even moist dirt but not mud. The problems arise from the different friction characteristics of different soils and surfaces. In conditions of a layer of slippery wet clay over a firm base, the tire will begin slipping at a very mild cornering lean angle, the transverse oriented center tread blocks are still carrying most of the tire weight, and because of their orientation to the side load, act like well lubricated skis in the lateral direction. They have little or no bite into the surface. By the time the side tread are carrying substantial weight, it is usually too late to stop the tire from slipping, the typical close spacing between the side treads just load up with mud and continue to slip. A tire called the "Porcupine" consists of high truncated conical tread blocks in the center section of the tire. Because of block flex, this tire feels very unstable on hard surfaces such as rock or gravel, tending to bounce over them with out providing good grip. But the relatively tall, round blocks penetrate the surface of mud very well and provide good grip in the soft conditions as well as not loading the relatively large spaces between the tread blocks with mud.